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122           MOEPHOLOGY AND EVOLUTION
parallel than in the adult (fig. 23, B). The maxillary premaxillary suture is straight, and passes through several foramina; and the anterior palatine foramina are separate or confluent. The suture may vanish in adult skulls ; but the suture between the maxillae may remain.
The posterior palatine foramina are on the horizontal parts of the palate bones. The posterior palatine spine is variable, being large, small or absent; and there are two small tubercles, one on each side of the middle line, between the posterior foramina, Owen (374) regards these eminences as characteristic of the Chimpanzee; so they help to distinguish it from the Gorilla.
The pterygoid fossae are long, narrow and deep, and the hamuli are long and slender.
There is no tympanic bulla. The glenoid fossa is shallow, but slightly concave from side to side. The endo-glenoid tubercle is of moderate size, but the post-glenoid process is small. The mastoid process is a rough ridge, but styloid and vaginal processes are usually absent. The Eustachian process is common as in the Gorilla.
The orifice of the carotid canal is more oblique than in the Orang, and the anterior condyloid foramina vary from one to three in number. In several skulls the number is different on the two sides. The jugular foramen is well marked.
The foramen magnum is situated far back on the basis cranii. It varies in outline in different skulls, but the shape cannot be regarded as an age or sex peculiarity. Probably it is an individual peculiarity.
The occipital condyles are small, and their long axes diverge at different angles in different skulls.